Cellular differentiation involves, at least in part, differential gene activity and control of the synthesis and degradation of given proteins (enzymes) at specific times and places in the various cells and tissues of the developing organism. One approach to studying genetic control mechanisms during development is to select a specific protein, or enzyme, as an indicator of the state of differentiation of a tissue or organ to analyze the factors that regulate its synthesis, properties, location and ultimate fate. The catalase system of maize is particularly well suited for this type of analysis. Many aspects of the genetic control and developmental regulation of catalase in maize have already been studied by this investigator. However, the precise mechanisms underlying the steps leading from genotype to the phenotype for the catalase-genes remain to be demonstrated. Elucidation of these mechanisms in a higher organism, especially one of agronomic importance such as maize, would have far-reaching implications for developmental genetics and for biology as a whole. We propose to use a combined genetic, biochemical and physiological approach to tackle this problem. The aim of the proposed work is to devise and execute experimental approaches which will help to elucidate some of the underlying mechanisms by which this system is regulated.